Problem: What is the slope of a line parallel to the line $2x - 4y = 9$? Express your answer as a common fraction.
The slope-intercept form of the equation of a line is $y = m x + b$ where $m$ is the slope.  So if we get $y$ on the opposite side from $x$ and make it have a coefficient of 1, the slope of the line will be the coefficient of $x$.  Thus we add $4y$ to both sides and divide everything by 4 which makes the coefficient of $x$ equal to $\boxed{\frac{1}{2}}$.